Conventionally, a piezoelectric coefficient d31 value of piezoelectric materials, such as PZT, <100> poled PMN-PT single crystals, is a half value of its piezoelectric coefficient d33. Due to reduced piezoelectric properties compared to the d33 mode, a heavy mass (large size sensors) or narrow bandwidth must be adapted to achieve high piezoelectric output. All the old solutions suffered from either lower piezoelectric output (high noise level) or reduced bandwidth when a senor was kept to the same size.